1. Field of the Invention
The present invention relates to a fuel injection valve for intermittent fuel injection into the combustion space of an internal combustion engine.
2. Discussion of the Background
A fuel injection valve is disclosed in EP-A-0 675 281 and U.S. Pat. No. 5,655,716. A control piston of a nozzle needle projects at the upper end into a control chamber. Above this control piston is arranged a valve, of which the valve body running coaxially to the control piston is guided laterally sealingly in the valve housing. The valve body projects with one end face facing the control piston into the control chamber and with the other end face into an additional chamber which communicates with an outflow line via a control valve and which is connected to the control chamber via a throttle bore leading through the valve body. This throttle bore and therefore the control chamber are permanently connected to the high-pressure part of the fuel injection valve via a transverse further throttle bore in the valve body. An annular chamber connected to the high-pressure part and running around the valve body is delimited at the top by a valve seat cooperating with the valve body.
When the nozzle needle is in the closed position, the control piston has a clearance in relation to the valve body, whereas, when the nozzle needle is in the open position, the control piston abuts the lower end face of the valve body. Immediately after the closing of the control valve, on the one hand, a pressure build-up initially occurs in the additional chamber through the transverse throttle bore, and, consequently, the valve body is moved toward the control piston and therefore brings about an automatic opening of the valve seat. As a result of this opening, an additional inflow of the control medium which is under high pressure flows into the additional chamber, with the result that the nozzle needle is brought into the closing position at increased speed by the valve body. After the closing position is reached, the valve body is moved back upward again by virtue of the pressure build-up in the control chamber and with spring-force assistance, until said valve body comes to bear on the valve seat.
EP-A-1 118 765 discloses a fuel injection valve for internal combustion engines, of which the needle-like injection-valve member has a stepped control piston which engages into a sleeve supporting a compression spring acting, as a closing spring for the injection valve. On the side facing away from the spring, the sleeve is supported an a control body which is arranged firmly in a housing of the fuel injection valve. The sleeve has a widening formed by a shoulder. In this widening, a sleeve-shaped valve body is arranged, a gap being present between the latter and the sleeve. The valve body interacts by its axial, end faces, on the one hand, with the shoulder, and on the other band, with the control body, the length of the valve body being slightly smaller than the clearance between the shoulder and the control body, so that the valve body can move back and forth in the axial direction over a small stroke. That part of the control piston which has a smaller diameter is guided in a narrow slitting fit in the valve body. Between that end of the valve body which faces away from the control body and that part of the control piston which has a larger diameter, an annular space is formed, which is connected to a high-pressure space arranged inside the housing and fed with fuel via a high-pressure inlet, via a gap which is formed between the corresponding part of the sleeve and that part of the control piston which has a larger diameter. A control space is delimited, on the one hand, by the control piston and, on the other hand by the control body and circumferentially by the sleeve-shaped valve body. A control passage having a narrowing acting as a throttle runs through the control body from the end face delimiting the control space to the apposite end face which delimits a low-pressure space. The control passage can be connected to the low-pressure space and can be separated from the latter by means of an electromagnetically actuated pilot valve.
A fuel injection valve is disclosed in EP-A-0 426 205. In this fuel injection valve, the control space is delimited circumferentially by the housing at the fuel injection valve and, as seen in the axial direction, on the one hand, at a double-acting control piston of the injection-valve member and, at the other hard, by an intermediate valve body, which leaves free an annular gap between itself and the housing, and the control body delimiting the annular gap and arranged firmly in relation to the housing. A compression spring is arranged between the control piston and the intermediate valve body. A stepped bore which exerts a throttle action runs through the intermediate valve body in the axial direction. A further bore runs, in the prolongation of this bore, through the control body and can be connected to a low-pressure space and separated from the latter by means of an electromagnetically actuated pilot valve. An additional bore issues into this bore running in the axial direction, in the control body, and is connected to a circumferential annular groove which is located in the control body and which is itself connected to the high-pressure inlet of the fuel injection valve. A plurality of bores run from this annular groove to that end face of the control body which faces the intermediate valve body. These bares are closed by the intermediate valve body when the latter comes to bear on the control body.
The disclosure of each of the above-noted prior art patents is herein incorporated by reference.